The tunnelling process is much slower, however.

"Aspirationally, we should be slightly faster than a snail," Musk said.

He explained that most tunnelling equipment moves 14 times slower than a snail, and hopes to match to snail-speed with The Boring Company.

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Musk tweeted a picture of a modified Tesla Model X nestled inside the tunnel, locked in by retractable wheel gears, which effectively turn it into a "rail-guided train."

Musk said that in future the tunnel loop might carry passenger cars on "skates" that whizz them through the tunnels, or that cars might eventually be fitted retractable side wheel, so they could travel through the tunnel autonomously.

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The Boring Company also released a video of a Tesla being whisked along inside the tunnel.